1. Field of the Invention
The present invention generally relates to a deposition method for forming a thin film on a processed substrate.
2. Description of the Related Art
Recently and continuing, as performance and function of semiconductor devices are becoming high, high integration of the semiconductor devices are being promoted and it is extremely desired that the semiconductor devices have fine structures. A technology for a wiring rule equal to or less than 0.10 μm has been developing. It is required for a thin film used for forming such a semiconductor device having high performance to have little impurity in the film and a high film quality such as a crystal orientation. Furthermore, it is desirable that the thin film have good coverage for forming on a minute pattern.
As a deposition method satisfying the above-discussed demand, an Atomic Layer Deposition method (ALD method) has been suggested. In this method, plural kinds of processing gas are mutually supplied one kind by one kind at the time of deposition, so that a deposition in a level close to an atomic layer or a molecular layer is implemented via adsorption of the process gas on a reaction surface. A thin film having a designated thickness can be obtained by repeating the above-mentioned steps.
The following steps are taken for implementing the deposition by the ALD method, for example. A process vessel having a first gas supply path for supplying first gas and a second gas supply path for supplying second gas, where a processed substrate is held inside thereof, is prepared. The first gas and the second gas are mutually supplied to the process vessel. More specifically, first, the first gas is supplied on the substrate in the process vessel so that an adsorption layer is formed on the substrate. Then, the second gas is supplied on the substrate in the process vessel so as to be reacted. This process is repeated a designated numbers of times as necessary. According to this method, since reaction with the second gas is done after the first gas is adsorbed on the substrate, it is possible to make a deposition temperature low. In addition, it is possible to obtain a high quality film having little impurity. Furthermore, it is possible to avoid forming a void due to reaction and consumption of the process gas at a hole in the upper part that is a problem in the conventional CVD method for depositing on the minute pattern, and therefore it is possible to obtain a good coverage property.
A film made of a first gas including a metal and a film made by using reduction gas of the first gas as a second gas so as to include the metal can be formed as a film formed by such a deposition method. For example, a film made of Ta, TaN, Ta(C)N, Ti, TiN, Ti(C)N, W, WN, W(C)N, or the like can be formed.
For example, a Ta(C)N film can be formed by using a chemical compound including Ta, such as Ta(NC(CH3)2C2H5)(N(CH3)2)3, as the first process gas and H2 as the second gas, and plasma-exciting H2 so that Ta(NC(CH3)2C2H5)(N(CH3)2)3 is reduced.
The film formed by such a deposition method is a high quality film and a good coverage property. Hence, for example, the film may be used as a Cu diffusion barrier film formed between an insulation film and Cu in a case where a Cu wiring is formed in the semiconductor device. See U.S. Pat. Nos. 5,916,365, 5,306,666 and 6,416,822, and U.S. Patent Application Publication No. 2002/0106846.
In a case where the thin film is formed by using the ALD method whereby the gasses are mutually supplied as discussed above, there is a problem in that it is difficult to optionally change a property of the formed thin film while the deposition whose film quality is good and having stable reproducibility can be done.
For example, it is difficult to change the composition of the formed film. For example, it is difficult to optionally change the content of C or N in the Ta(C)N film.